Apparatus and method for introducing small amounts of refractory elements into a vapor deposition coating

ABSTRACT

A method of introducing small amounts of a refractory element into a vapor deposition coating. A second material ( 30 ), containing at least two elements which are desired to be deposited as a coating on a base material, has placed over it a first material ( 20 ) substantially comprising such two elements and a refractory element. The first material ( 20 ) is adapted to permit transport of the at least two elements in the second material ( 30 ) through the first material ( 20 ) when the first ( 20 ) and second ( 30 ) material are in a molten state and in touching contact with the other so as to permit evaporation of the two elements and the refractory element from an exposed surface. Heat is supplied to the first ( 20 ) and second ( 30 ) materials to permit evaporation of the at least two elements of second material ( 30 ) and the refractory element in the first material ( 20 ), and the resulting vapors are condensed as a deposit on a base material ( 50 ). A particular method of heating is further disclosed to assist in maintaining adequate rates of evaporation for the aforesaid method, wherein the supplied heat is supplied to an inner heated area ( 91 ) and a surrounding outer heated area ( 92 ) and at least a portion of the inner heated area ( 91 ) is heated to a greater temperature than the outer heated area ( 92 ).

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a vapor deposition apparatus andmethod for applying a coating to a base material, and more particularlyto a vapor deposition apparatus and method wherein small amounts ofrefractory elements are incorporated into a vapor deposition coating.

[0002] The thermal evaporation and condensation of solid materials suchas metals to form a coating on a base material, commonly referred to asvapor deposition, is a relatively developed art. There are manysophisticated prior art techniques and apparatuses which permit suchmaterials to be evaporated from a source and condensed to form a coatingor layer on a substrate disposed a distance from the source. Suchprocesses all involve heating a material to be evaporated to atemperature at which it has a significant vapor pressure, thus creatinga vapor stream. Heating techniques include direct methods, such asheating the material to be deposited using resistance, induction,electron beam or laser beam means to melt all or some portion of thematerial to be evaporated, or indirectly, such as by heating the surfaceof a higher melting material and flashing the material to be evaporatedoff the hot surface. The evaporated material thereafter becomescondensed on the surface of the base material, thereby providing acoating thereon.

[0003] Refractory materials are often desired to be incorporated intocoatings applied to the surface of components exposed to hightemperatures, such as gas turbine components used inter alia in aircraftengines, to act as a protective coating in a process known as thermalbarrier coating (TBC). Methods for depositing ceramic barrier coatingslike zirconia (i.e. zirconium oxide) which serve as thermal barriercoatings are known in the art. For example, U.S. Pat. No. 5,773,078 toSkelly, commonly assigned to the assignee of the present invention,namely General Electric Company, discloses an improved method fordepositing zirconium oxide from a zirconium oxide source onto a basematerial by means of physical vapor deposition, comprising the step ofadding zirconium metal to a zirconium oxide ingot as the ingot isheated. Despite the improvements realized by the method of U.S. Pat. No.5,773,078, use of a rare earth metal oxide such as zirconium oxide as anevaporant source causes problems due to release of the oxygen present inthe oxide and difficulties in regulating the uniformity of compositionin the resulting deposited condensate.

[0004] Where the starting material to be evaporated and applied as acoating to a base material is a multi-constituent alloy, other problemsare encountered. In particular, the composition of the coated materialwhen applied by the vapor deposition method as described frequently andundesirably was substantially different than the composition of thestarting material, and/or the condensate would not have a uniformcomposition through its thickness which closely resembled that of thestarting material. These problems were directly due to the fact that therates of evaporation of elements contained in the multi-constituentstarting material alloy are related to their vapor pressures at thetemperature of the evaporation source. In the case of alloys,particularly multi-constituent alloys, one or two elements thereoftypically have significantly higher vapor pressures than the others,such that the condensate is richer than the starting material in theseelements. If the material being evaporated has a fixed volume and isentirely evaporated, the condensate will have a non-uniform compositionthroughout its thickness, but will reflect, in a macroscopic sense, thestarting composition of the material. If the starting material iscontinually replenished, such as by maintaining a constant pool volume,the composition of the condensate will be higher throughout itsthickness in the elements which have higher vapor pressures.

[0005] U.S. Pat. No. 5,474,809 to Skelly et al, assigned to GeneralElectric Company who is the common assignee with respect to the presentinvention, expressly recognized the problems of the prior art inachieving uniform and desired composition for the coating closelycorresponding to that of the evaporated material. Such patent discloseda method for carrying out vapor deposition that achieved a coating on abase material which closely resembled the composition of the starting(i.e. evaporated) material, that is to say the coating purportedly tocontain substantially the same elements in substantially the sameproportions as the starting material, even if the starting material wasa multi-constituent alloy having elements each of significantlydifferent vapor pressures. In particular, the aforementioned Skelly etal patent disclosed a method of making an evaporated deposit of amaterial using the vapor deposition process, wherein one material (asecond material) having a composition which was desired to be formed asa coating on a base material, is overlaid by a first material whichconsisted of a refractory material with a higher melting point or avapor pressure at an elevated temperature that is less than each of theconstituents of the second material. Accordingly, upon heating of thefirst material the underlying second material becomes melted, and theconstituent elements of the second material proximate the overlyingfirst material are transported by convection and thermal mixing throughthe first overlying material and thereafter evaporated from the surfaceof the first overlying material. In such process the first materialbecomes molten and transmits heat downwardly to the underlying secondmaterial, thereby forming a molten zone therein, and second material insuch molten zone therein becomes mixed with the molten zone of firstmaterial immediately above it, permitting the second material to beevaporated from the surface thereof. Advantageously, such processpurportedly permits coatings to be formed on a base material having acomposition which is substantially identical to that of the secondmaterial. The second material (or at least certain of the elementstherein) which were desired to be evaporated possessed vapor pressureswhich permitted such elements to be preferentially evaporated incomparison to the first material. Accordingly the deposit containedquantities of the second material, but no or only minute trace amountsof the first material (less than 0.05 atomic percent).

[0006] In the case of refractory materials in the form of rare earthmaterials such as zirconium or hafnium intended to be incorporated intoa thermal coating for deposit on a base material, it is actuallydesirable for such materials to be evaporated and thereby incorporatedin the deposited coating where a thermal barrier coating is desired tobe applied. However, when rare earth metals, such as zirconium orhafnium are used in the process of Skelly et al described in U.S. Pat.No. 5,474,809 as the first material, and metal alloys such as anickel-aluminum alloy is used as the second material, it is found thatthe method taught by Skelly et al is physically unworkable. In thisregard, when employing a rare earth metal, such as zirconium, as thefirst material using the method taught by Skelly et al, such firstmaterial when melted tends to “ball-up” when heated by a heat sourcesuch as an electron beam, by virtue of the surface tension forcesexisting between molten zirconium and the solid second material. As aresult there is little or no proper transfer of heat downwardly to theunderlying second material to form a molten zone there within so as topermit molten second material to migrate upwardly there through andthereafter evaporate from the surface. In such circumstances, neitherthe underlying second material or the zirconium which comprises thefirst material becomes evaporated so as to form a deposit. Moreover, inSkelly et al even where the first material is not a rare earth metal,the Skelly et al patent did not develop or disclose any circumstances inwhich it was capable of obtaining quantities of the refractory metal inthe deposit in concentrations greater than trace amounts (i.e. greaterthan 0.05 atomic percent).

BRIEF SUMMARY OF THE INVENTION

[0007] A workable vapor deposition apparatus and method forincorporating greater than trace amounts of refractory materials such aszirconium and hafnium metals into coatings on base materials for use asthermal barrier coatings and the like is disclosed and claimed.

[0008] The present invention in one of its broad embodiments consists ofa method of forming a deposit on a base material, such deposit having atleast two elements from a second material and small amounts of arefractory element selected from the group of refractory elementscomprising zirconium, hafnium, yttrium, titanium, rhenium, silicon,chromium and alloys thereof, comprising the steps of:

[0009] selecting a first material comprising said at least two elementsfurther alloyed with said refractory element, said second materialcomprising said at least two elements, said first material adapted topermit transport of said at least two elements in said second materialthrough said first material when said first and second material are in amolten state and in touching contact with one another so as to permitevaporation of said two elements and said refractory element from anexposed surface thereof;

[0010] placing a quantity of said first material over a quantity of saidsecond material in a crucible means so that the first material at leastpartially covers the second material;

[0011] supplying heat to the first material sufficient to create amolten zone within and through the first material such that the moltenzone of the first material is in touching contact with the secondmaterial to thereby create a molten zone within the second material,wherein said two elements in the second material are transported throughthe molten zone rich in the first material and said refractory elementand said two elements are each evaporated therefrom thereby forming avapor stream; and

[0012] collecting condensate from the vapor stream as a deposit on thebase metal.

[0013] The method of the present invention, where the first materialcomprises a refractory material having a high melting temperature suchas titanium, zirconium, or hafnium or alloys thereof, has the unexpectedand surprising result that, contrary to what would be expected from theteachings of Skelly (if such could be practiced without the “balling up”of the rare earth metal, discussed supra) more than trace amounts,namely small amounts and amounts over 0.05 atomic percent of therefractory element may be incorporated into the deposit. In particular,and advantageously, the method of the present invention by providing arefractory element that is alloyed with at least two of the sameelements that are intended to be evaporated and form part of thedeposit, and further by ensuring that sufficient amounts of refractoryelement is present in the first material, is able to overcome not onlythe “balling up” difficulties of refractory rare earth metals, butfurther, in contrast with the result obtained by the method disclosed inU.S. Pat. No. 5,474,809 to Skelly et al, obtain a deposit having greaterthan simply trace amounts of a refractory material. For the purposes ofthis document, the definition of trace amounts is the same as adopted inthe Skelly et al patent, namely atomic percentages equal to or less than0.05 atomic percent.

[0014] In practicing the method of the present invention, it isnecessary that sufficient quantities of the refractory material bepresent in the first material in order to produce a deposit containingmore than trace amounts of refractory material (i.e. more than about0.05 atomic percent.) It has been found at least from experimentalresults to date that the atomic percentages of refractory materialpresent in the first material is not particularly directly related tothe amount of refractory material present in the deposit, at least forthe range of atomic percentages tested, namely the range of 33%-76%(a/o) of refractory element present in such first material, these rangesbeing the preferred ranges. Rather, the presence of refractory materialin atomic percent in the deposited coating appears more related to thephysical quantity of refractory material in the first material inproportion to the underlying second material. In other words, there issome indication from the experimental results, while not always holdingtrue, that the greater the physical quantity of refractory material andthus the greater the quantity first material physically covering thesecond material when enclosed in a crucible, the greater the quantity ofthe refractory element present in the deposit. However, because thisgeneralization does not appear to always hold true, some experimentationas to the amount of refractory material present in the first materialfor a given coverage of the second material of a given dimension may berequired in order to arrive at a physical amount of refractory materialwhich need be present in the first material in order that the depositcontain greater than trace amounts of such refractory material.

[0015] It has been found it is beneficial (although not a requirement)that the first material contain the same two elements in the samerelative atomic percentages as in the second material, in order toassist in uniformity of composition of the deposited coating and also topermit the coating composition to more closely match that of the secondmaterial. Accordingly, in a first preferred embodiment, the two elementspresent in the second material (which in the preferred embodiment arenickel and aluminum) are present in approximately equal ratios to eachother. Likewise in another preferred embodiment, the two elementspresent in the first material are also present therein in approximatelyequal ratios. Preferably, as mentioned above, the two elements presentin both the first material and the second material are present in equalratios in each of the first and second materials, with such ratio beingapproximately 50-50 (a/o) in the preferred embodiment.

[0016] The refractory material is preferably comprised of eitherzirconium, hafnium, yttrium, rhenium, silicon, chromium, titanium oralloys thereof, although other refractory materials or alloys thereofmay be used. Where the deposited coating applied by the above method isintended to be a thermal barrier bond coating, in a preferred embodimentthe first material is formed of a rare earth metal such as zirconium orhafnium. Two elements found suitable for these purposes and for alloyingthereto in the first material and being present in the second materialare nickel and aluminum, and in a further preferred embodiment, thenickel and aluminum exist in alloy in the second material and also inthe first material in an approximate molar ratio of 1:1.

[0017] Advantageously, using the aforesaid preferred method of thepresent invention, refractory material may be uniformly deposited on abase material in concentrations exceeding nominal percentages (i.e.exceeding 0.05 atomic percent).

[0018] As a further consideration, it has been found that when pure rareearth metals, such as zirconium and hafnium are used as the refractoryelement, upon being heated have a tendency to form oxide skins. Theseoxide skins not only have higher melting points than the pure rare earthmetals but also further tend to reduce the rate of evaporation of suchrare earth metal thus slowing the rate of deposition of any condensate.These oxide skins, due to the higher melting points, greatly reduce theevaporation of rare earth metals, with the result that any depositsformed are virtually devoid of rare earth elements therein.

[0019] Accordingly, in a further aspect of the method of the presentinvention where the refractory element is a rare earth metal, aparticular manner of heating is disclosed in order to obtain a depositwith more than simply trace concentration of rare earth metals. Inparticular, when carrying out the step of supplying heat to said firstmaterial, such step comprises supplying heat to an inner heated area anda surrounding outer heated area, wherein at least a portion of saidinner heated area is heated to a greater temperature than thesurrounding outer heated area. In a preferred embodiment, where anelectron beam is used as a means of heating, such heating step comprisesdirecting an electron beam across the first material, furthercomprising:

[0020] directing such a beam across the inner heated area; and

[0021] directing such a beam across the outer heated area; and

[0022] providing a scanning pattern effective to transiently increasetemperature of a least a portion of said inner heated area above that ofsaid outer heated area so as to transiently increase vaporization fromsaid at least a portion of said inner heated area.

[0023] The mechanics of how a heating pattern such as that disclosedherein is able to increase the rate of evaporation is not entirelyknown. It is theorized that by heating the inner heated area to atemperature greater than the surrounding outer area, that convectioncurrents, in particular Maragoni flow patterns, are created in themolten zone, which divert oxide layers which may form at the upperexposed surface to the outer edges of the molten zone surface, therebyleaving unoxidized molten material, including rare earth metal,proximate the inner heated zone surface which can then be betterevaporated from the hottest part of the molten material and thereaftercondensed on the base material to thereby form the coating.

[0024] A base material or article having a coating deposited thereon bythe method of the present invention is also disclosed. Advantageously,coatings applied to articles by the method of the present inventionpossess refractive material therein in excess of nominal percentages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The method and apparatus by which the method of the presentinvention may be practiced will now be described with reference to theaccompanying drawings showing preferred (non-limiting) embodiments, inwhich:

[0026]FIG. 1 is a schematic diagram of a preferred apparatus used forperforming the method of this invention; and

[0027]FIG. 2 is a “cut-away” illustration of a crucible containing thesecond material and an overlying first material “hot top” comprising therefractive material which is desired to be coated on a base material;

[0028]FIG. 3 is an illustration of a preferred electron beam scanningpattern for use where the refractory material is a rare earth metal; and

[0029]FIG. 4 is a schematic view of a cross section through the moltenzones in the crucible means during heating of the material therein usinga particular heating pattern.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The method of this invention may be practiced in conventionalapparatuses of the type that are commonly used for thermal or electronbeam evaporation processes.

[0031]FIGS. 1 & 2 show an apparatus 10 for forming a condensed deposit40 on a base material 50 using vapor deposition method of the presentinvention, where such deposit 40 contains small amounts of a refractoryelement. The apparatus 10 is used for applying a coating 71 to a basematerial, for such uses as thermal barrier coatings and/oranti-corrosive coatings, and the like, wherein the coating containssmall amounts of a refractory element, such as zirconium, hafnium,rhenium, silicon, yttrium or other rare earth metals, or titanium, orchromium.

[0032] An airtight housing enclosure 12 is provided which may beevacuated of air, so as to permit the vapor deposition process toproceed in absence of potential contaminants and/or potentialundesirable reactants. In this regard, a combination of stagedmechanical, cryogenic, turbomolecular, and/or diffusion pumps may beused for the purposes of evacuating the housing enclosure 12. A cruciblemeans 45 is situated within housing enclosure 12. For the evaporation ofmetal alloys through a molten pool 56, a water-cooled copper crucible ofa type well known in the art is preferred. The crucible means 45 is usedto contain the materials to be evaporated during the evaporationprocess. Such crucible means 45 may have a bore 46 which permits secondmaterial 30 in the form of a solid bar or ingot to be fed continuouslyor semi-continuously therethrough into crucible means 45. The ingot feedrate can be controlled so as to keep the molten pool surface 57 at aconstant level, which may be desired where it is necessary tocontinuously maintain deposition of substrate deposit 40 at fixedvertical distances above the molten surface 57.

[0033] Heating means, which in the preferred embodiment of the inventioncomprise one or more electron beam guns 60, are provided for supplyingheat necessary to liquefy at least a first material 20 and a portion ofan underlying second material 30 which is present within the cruciblemeans 45. Such electron beam guns 60, are well known in the art, causeevaporation of at least certain elements on the molten metal surface 57within crucible means 45 to thereby form a vapor stream 70. The electronbeam guns 60 may be provided with various automatic control patterns toadjust the energy supplied to the material, or to the effect a specificscanning/heating pattern, and in the preferred embodiment are providedwith such automated control mechanisms to provide a particular heatingpattern as hereinafter described to assist in maintaining a desired rateof material deposition on base material 50.

[0034] The method of the invention for forming a deposit 40 on a basematerial 50 will now be described. A first material 20 is selected,comprising a refractory element selected from the group of refractoryelements comprising zirconium, hafnium, yttrium, titanium, rhenium,silicon, and chromium, which is alloyed with at least two additionalelements. In the preferred embodiment such at least two elements arenickel and aluminum which form the major components of a nickel-basedalloy, which is desired to be deposited along with a refractory elementon a base material 40. However, other two (or more) predominant elementcombinations found in other alloys, such as Ti-base, Fe-base, andAl-base alloys, may also be used where the predominant elements of suchalloys, along with a refractory element, are desired to be deposited asa coating 71 where such predominant elements are deposited insubstantially the same ratios as exist in the alloy so as to result in acoating 71 having substantially the same elemental composition inapproximately the same molar ratios as the material being evaporated,save and except for the further addition of small amounts of arefractory element.

[0035] A second material 30 is likewise selected, which also comprisesthe same two elements, such two elements intended to be evaporated andultimately form the bulk of the deposit 40 which forms a coating 42 onbase material 50. By selecting a first material 30 wherein the same twoelements that are present in the second material 30 are also present inthe first material 20 along with the refractory material, the applicantshave found that two important advantages are realized. Firstly, wherethe refractory elements is a rare earth such as zirconium, the alloyingof zirconium with such at least two elements overcomes the “balling up”problem if simply a pure refractory element, namely a rare earth metalsuch as zirconium, were used as the first material 20. Such alloyingthereby permits the first material 20, upon being heated, to liquefy andadvantageously spread over the second material 30, as shown in FIG. 1,rather than becoming “balled up”. In such manner the molten alloymixture is thereby able to transmit heat downwardly so as to cause amolten zone 56 to appear in second material 30, and allow the method ofthe present invention to be performed and result in a deposit havingsuch refractory material therein. Secondly, by including the same twoelements in the first material 20 as those which are (principally)contained in the second material 30, more uniform deposits and depositshaving compositions more closely resembling the original startingmaterial (i.e. second material 30) which is desired to be deposited areable to be obtained.

[0036] Once the first material 20 and second material 30 are selected, aquality of second material 30 is placed in crucible means 45.Thereafter, a quantity of the first material 30 is placed over thequantity of the second material 30 in the crucible means 45 so that thefirst material at least partially covers the second material 30.Thereafter, a base material 50 is situated in a vertically disposedposition immediately above the crucible means 45, and the housingenclosure 12 evacuated of air. Heat is then supplied to the firstmaterial 20 sufficient to create a molten zone 55 within and through thefirst material 20 such that the molten zone 55 of the first material 20is in touching contact with the second material 30 to thereby likewisecreate a molten zone 56 within the second material 30, wherein the atleast the two elements in the second material are transported throughthe molten zone 55 rich in the first material 20, and the refractoryelement and the two elements are each evaporated therefrom forming avapor stream 70. Such vapor stream 70 is condensed on base material 50to form deposit 40 thereon. After a period of time such deposit 40 formsa coating 71 containing the at least two elements from the secondmaterial and the refractory element from the first material 20.

[0037] The heating of the first and second material 20, 30 respectivelyin the crucible means 45 may be accomplished by suitable heating means,including known means such as resistance heaters, induction heatingcoils and electron beam guns. In the case of high temperature firstmaterials 20, and in particular where rare earth metals such aszirconium are used as the refractory element in the first material, anelectron beam gun or guns 60 are preferred as the heating means. Usingelectron beam guns 60 one or more electron beams 68 can be rastered overthe surface 57 of the first and second material 20, 30 in a variety ofpatterns which can assist mixing of the molten materials, and has theadditional added advantages (such as in the case of heating of rareearth metals where oxide layers may tend to form) in creating Maraganiflow patterns (see FIG. 4) within the molten zone 55 and 56 which assistin maintaining and preventing a decrease in the rate of refractoryelement evaporation from surface 57.

[0038] With respect to preferential rastering patterns, the applicantshave found that a specific rastering pattern advantageously,particularly where the refractory element is a rare earth metal such aszirconium prone to oxide layer formation, maintains continuousdeposition rates and thus assists in obtaining commercially viable ratesof deposition of a coating 71 on a base material 50. In this regard, theapplicants have found that a heating method useful in combination withthe method of the present invention, wherein heat is supplied to aninner area 91 and a surrounding outer heated area 92 wherein at least aportion of the inner heated area 91 is heated to a greater temperaturethan the outer heated area 93, is advantageous in maintainingcommercially viable deposition rates.

[0039] With respect to this particular heating pattern, reference is tobe had to FIGS. 2-4 inclusive. In particular, in a preferred embodimentof this invention, an electron beam gun 60 and electron beam 68 are usedto accomplish such heating pattern, wherein the electron beam or beams68 from the electron beam gun(s) 60 are directed across both an innerheated area 92 and an outer heated area 93, and the scanning pattern ofsuch electron beam or beams 68 is such to transiently increase thetemperature of at least a portion of an inner heated area 92 above thatof the outer heated area 93 so as to transiently increase vaporizationfrom the portion of inner heated area 92. (See FIG. 2 & 3).

[0040] In the preferred embodiment, circular electron beams 68 are used,which may be provided from a single electron beam gun 60 or two or moreguns 60. In the preferred embodiment a single beam 68 from beam gun 60provides a circular beam 68 a of diameter ‘a’, and is moved in acircular pattern so as to heat an inner circular area 92 of diameter‘2x’. (See FIG. 3) Likewise, a second electron beam gun 60 is providedto provide a circular beam 68 b, of diameter ‘y’, which is likewisemoved in a circular motion to heat a circular area 93. The two electronbeams guns 60 are cycled so that beam 68 a temporarily, due to eitherhigher beam power or more frequent cycling times, transiently increasesthe temperature of a portion or all of inner heated area 92 over outerheated area 93. It is accordingly believed that such heating patterntransiently increases the vaporization from the inner heated area 92over the outer heated area 93, so as to create Marangoni flow patterns97 within the molten zones 55 and 56 of the first and second materials20, 30, thereby increasing mixing between the two zones, 55 and 56 andfurther causing any oxide layers which may tend to form on surface 57 tomigrate from the inner heated area 92 radially outwardly from the centerof the molten pool 55 to the outer heated area 93, thereby leaving theinner heated area 92 free of oxide layer at the surface 57 and therebypermitting evaporation of both elements from the second material 30 andthe refractory element from the first material 20 (see FIG. 4).

[0041] Other heating patterns to accomplish the transient heating of aninner heated area 92 over an outer heated area 93 will immediately occurto persons skilled in the art. The invention is not limited to theparticular circular heating patterns disclosed herein and in particularthe circular heating pattern shown in FIGS. 2 & 3.

[0042] Apparatus 10 may also comprise a replenishment means forreplenishing any minor amounts of material that are lost during theprocess of evaporation. Other additional elements may also beincorporated into apparatus 10 by those of ordinary skill to facilitatethe practice of the method of this invention such as automated controlsfor the feed of replenishment means and second material, deposition ratesensors for incorporation into feedback controllers, means for modifyingthe vapor stream 70 such as by addition of various electrical potentialsand other elements. Further, other elements or compounds may also beintroduced back into housing enclosure 12 in order to react with one ormore of the elements present in vapor stream 70 or condensate 50. Suchelements or compounds could include oxygen, nitrogen, methane or otherreactive species in the case of the evaporation of metal alloys.

[0043] The present invention will be described in further details withreference to the following non-limitative examples. In each of examples1-17 set out below, a circular sample of second material 20 in the formof a 1″ diameter Ni—Al alloy of composition as hereinafter described wasused. A two-circle electron beam heating pattern, as shown in FIG. 3,was used to heat the material placed in the crucible, for examples 15and 16. In all other examples a single circle electron beam pattern of1″ diameter heated area was used, using the same power as the two-circleheating pattern. In all cases single electron beam 68 provided a singlebeam of ¼″ diameter, of approximately 30 kV at 0.67-1.0 amps, (i.e.,20-30 kW) which was directed at the rare earth metal “hot top”. The hottop was heated to incandescence and caused to melt. For the two-circleheating method, the beam 68 was directed within the inner circle ½″diameter inner heated area 92 for 400 milliseconds, and rotated aboutand within the inner heated area 92 (See FIG. 3) of area B (¼″)² duringa 12.5 millisecond period, thereby repeating 400/12.5=32 times.Thereafter the beam was directed to the outer heated circular area 93,as shown in FIG. 3, of scanned area B×[(½″)²−(¼″)²] (see FIG. 3) for 200milliseconds. The beam 68 was then directed around the outer heated areaover a period of 12.5 milliseconds, and accordingly repeated 200/12.5=16times. The beam was then directed back to the inner circle area 92, andthe process continually repeated.

[0044] Composition of the resulting substrate for each of examples 1-17was determined by electron microprobe analysis, and is shown in Tables I& II below. In all cases the composition of the deposit on the basematerial was taken from a position vertically above the longitudinalaxis of the cylindrical ingot placed within crucible means 45.

EXAMPLE 1

[0045] Three (3) 3.5 gram disks of substantially pure rare earth metal(zirconium) “hot top”, each approximately 1 inch in diameter byapproximately {fraction (1/16)} inch thick which formed thefirst-material 20, were placed on top of so as to substantially cover a1″ diameter×6 inch length ingot which formed the second material 30.Such ingot was comprised of nickel 50%-aluminum 50% (all amounts inatomic weight percent). A base material 50 was disposed directly abovethe “hot top” so as to provide a surface for any vapors to condense on.

[0046] An electron beam of 20 kV at 0.67-1.0 amps, (i.e., 20-30 kW) wasdirected at the rare earth metal “hot top”, and the hot top heated toincandescence so as to cause it to melt. Upon melting, the rare earthmetal “hot top” changed its shape from a disk to a sphere. Theunderlying second material ingot did not melt or form a melt pool. Nozirconium was observed after such process on the surface of the basematerial 50 as determined by electron microprobe analysis.

EXAMPLE 2

[0047] Four 3.5 gram disks of substantially pure rare earth metal(zirconium) “hot top”, each approximately 1 inch in diameter byapproximately {fraction (1/16)} inch thick, were placed on top of so asto substantially cover 1 inch diameter by approximately 6 inch in lengthingot which formed the second material. Such ingot was comprised anickel 50%-aluminum 50% (all amounts in atom percent). A base materialwas disposed directly above the “hot top” so as to provide a surface forvapors to condense on.

[0048] An electron beam of 25 kV at 0.67-1.0 amps, (i.e., 10-20 kW) wasdirected at the rare earth metal “hot top”, and the hot top heated toincandescence so as to cause it to melt. Upon melting, the rare earthmetal “hot top” changed its shape from a disk to a sphere. Theunderlying second material ingot did not melt or form a melt pool. Nozirconium was definitively detected after such process on the surface ofthe base material as determined by electron microprobe analysis.

EXAMPLES 3-8

[0049] In each of examples 3 through 8, a first material “hot top” wasformed, comprised of nickel 33%-aluminum 33%-zirconium 33% (all amountsin atom percent), with the weight (in grams) which were contained in thehot top (first material) shown in Table 1, below. The second materialingot comprised of nickel 50%-aluminum 50% (all amounts in atompercent). In each of these examples, the molten pool was heated by asingle circle electron beam raster, scanning a 1″ diameter area.

[0050] The hot top alloy was melted by the electron beam, and formed acontinuous pool of zirconium-rich liquid, causing a substantial portionof the underlying nickel-aluminum ingot, which lay beneath such not-topto then melt. A raft of zirconium-rich liquid initially appeared on thetop surface, and was distinguished by its bright white color compared tothe characteristic orange color of the molten nickel-aluminum. This isbelieved to be due to zirconium having a higher emissivity thannickel-aluminum. During the course of several minutes (approximately10-15 minutes), the white raft slowly disappeared, as the zirconiumbecomes completely mixed with the nickel-aluminum liquid from thefeedstock ingot (second material). The concentration of zirconium founddeposited on the base material were as set out in Table I below.

EXAMPLES 9-13

[0051] In each of these examples, save example 12 & 13 where thecomposition comprised Ni 18-Al 18 Zr 64, and Ni 12-Al-12 Zr 76,respectively, the first material comprised a nickel 33%-aluminum33%-zirconium 33% (all amounts in atom percent) hot top. In Example 9,the second material was comprised of nickel 45%-aluminum 55% (allamounts in atom percent) ingot, whereas in Examples 10-13, the secondmaterial was comprised of nickel 50%-aluminum 50%-(all amounts in atompercent).

[0052] Composition of the resulting condensate on the substrate for eachof Examples 9 through 13 was determined by electron microprobe analysis.The concentration of zirconium in the condensate is shown in Table Ibelow. TABLE 1 Starting Material Composition Hot Top Grams of Exp. No.(a/o) Composition refractory Melt Pool Substrate Composition (Example(i.e., second (a/o) (i.e., first material (Zr) Composition (a/o) (a/o)No.) material) material) in Hot Top Ni Al Zr Ni Al Zr E 161 (1)Ni50-Al50 3 Zr disks 10.5 70.1 ± 0.5 26.8 ± 0.2 0.03 ± 0.04 E 173 (2)Ni50-Al50 4 Zr disks 14.0 59.3 ± 3.4 40.6 ± 2.3 0.03 ± 0.02 E 189-2Ni50-Al50 Ni33-Al33- 13.0 — — — 61.7+/−0.6 38.2+/−0.6 0.10+/−0.04 (3)Zr33 E 189-4 Ni50-Al50 Ni33-Al33- 13.0 — — — 63.4+/−0.6 36.4+/−0.90.16+/−0.12 (4) Zr33 E 196 Ni50-Al50 Ni33-Al33- 14.0 — — — 62.9+/−0.839.0+/−1.8 0.02+/−0.02 (5) Zr33 E 290-1 Ni50-Al50 Ni33-Al33- 15.2 — — —52.4+/−2.4 40.0+/−3.0 0.02+/−0.04 (6) Zr33 E 291-1 Ni50-Al50 Ni33-Al33-15.2 — — — 48.3+/−3.2 39.7+/−1.9 0.01+/−0.01 (7) Zr33 E 289-2 Ni50-Al50Ni33-Al33- 15.2 — — — 52.0+/−1.1 39.8+/−1.5 0.02+/−0.09 (8) Zr33 E 286Ni45-Al55 Ni33-Al33- 15.5 — — — 61.0+/−6.6 38.8+/−6.8 0.06+/−0.09 (9)Zr33 E 181- Ni50-Al50 Ni33-Al33- 25.7 22.3 3.3 73.3 60.7+/−2.833.3+/−2.0 5.01+/−1.03 10(10) Zr33 E 255-5 Ni50-Al50 Ni33-Al33- 32.516.7 3.7 78.7 57.4+/−0.9 39.5+/−2.1 2.46+/−1.47 (11) Zr33 E 180-8Ni50-Al50 Ni18-Al18- 41.3 16.0 2.6 81.2 59.8+/−3.9 35.3+/−4.64.36+/−1.77 (12) Zr64 E179- Ni50-Al50 Ni12-Al12- 46.6 30.6 4.7 64.657.2+/−4.9 38.5+/−6.3 3.81+/−4.71 10(13) Zr76

[0053] TABLE II Grams of Starting Material Hot Top refractoryComposition (a/o) Composition material Substrate Composition Exp. No.(i.e., second (a/o) (i.e., first (Zr) in Hot Electron (a/o) (ExampleNo.) material) material) Top Beam Pattern Zr E 379 (14) Ni50-Al50Ni33-Al33- 15.32 1 circle 0.01-0.02 Zr33 E 380 (15) Ni50-Al50 Ni33-Al33-15.52 1 circle 0.01-0.02 Zr33 E 381 (16) Ni50-Al50 Ni33-Al33- 15.37 2circle 0.20-0.25 Zr33 E 387 (17) Ni49-Al-49-Cr2 Ni33-Al33- 15.57 2circle 0.30-0.72 Zr33

EXAMPLES 14-15

[0054] Examples 14 & 15 utilized a 1 circle electron beam raster, likeexamples 1-13, with a first material having a Ni33-Al33-Zr33 composition(a/o), and the second material a Ni50-Al50 composition. Obtainedsubstrate composition is shown in Table II.

EXAMPLES 16-17

[0055] In examples 16-17, the molten pool was heated by a two circleelectron beam raster, as described previously the electron system whichdrove these two electron beam patterns switched continues from the innercircle to the outer circle, then returning to the inner circle, andrepeating this pattern.

[0056] As may be seen from examples 10-13, where sufficient zirconiumwas present in the first material 20, zirconium concentrations wereobtained in the coating 71 in concentrations in excess of 0.05 atomicpercent. Likewise, with respect to Examples 16 & 17, where a two—circlerastering pattern was utilized, such produced greater concentrations ofzirconium in the coating 71 than for examples where equivalent amountsof zirconium were used, but only a single circle raster pattern was used(e.g. compare with examples 5-8).

[0057] It will be understood, of course, that modifications can be madein the embodiments of the invention described herein without departingfrom the scope and purview of the invention. For a complete definitionas to the scope of the invention, reference is to be made to theappended claims.

We claim:
 1. A vapor deposition apparatus (10) adapted to deposit avapor-deposited coating (71) containing a refractory element in greaterthan trace amounts, said vapor deposition apparatus comprising: a) avapor deposition source material, said vapor deposition source materialcomprising a first material (20), said first material comprising atleast a first element and a second element, said refractory elementbeing alloyed therewith, and a second material, said second material(30) comprising at least a third element and a fourth element; b) acrucible (45) having an open top, said crucible being capable ofcontaining said vapor deposition source material, wherein said vapordeposition source material is disposed in said chamber such that saidfirst material is positioned over said second material and at leastpartially covers said second material; c) a base material (50) locatedvertically above said open top; and d) at least one heating means (60),said heating means being capable of supplying sufficient heat to createa molten zone (55) in said first material, wherein said molten zone (55)contacts said second material (30), thereby creating a second moltenzone (56) in said second material (30), whereby said third element andsaid fourth element in said second material and said refractory materialare evaporated from said crucible (45), thereby forming a vapor streamthat impinges upon said base material (50) and condenses thereon,thereby forming said vapor-deposited coating (71) containing saidrefractory material, said third material, and said fourth material. 2.The vapor deposition apparatus of claim 1, further including an airtightenclosure (12), said airtight enclosure being capable of beingevacuated, wherein said crucible (45), said first material (20), saidsecond material (30), said heating means (60), and said base material(50) are disposed within said airtight enclosure (12), whereby saidvapor-deposited coating may be deposited in the absence of potentialcontaminants or reactants.
 3. The vapor deposition apparatus of claim 2,further including a means for evacuating said airtight enclosure (12).4. The vapor deposition apparatus of claim 3, wherein said means forevacuating said airtight enclosure is a combination of staged mechanicalpumps, cryogenic pumps, turbomolecular pumps, and diffusion pumps. 5.The vapor deposition apparatus of claim 2, further including a reactivegas inlet for providing a reactive gas to said airtight enclosure. 6.The vapor deposition apparatus of claim 5, further including a reactivegas source coupled to said reactive gas inlet.
 7. The vapor depositionapparatus of claim 6, wherein said reactive gas is selected from thegroup consisting of oxygen, nitrogen, and methane.
 8. The vapordeposition apparatus of claim 1, wherein said heating means (60) iscapable of heating an inner area (91) and an outer area (92) of saidvapor deposition source material such that said inner area (91) isheated to a greater temperature than a temperature of said outer area(92).
 9. The vapor deposition apparatus of claim 1, wherein said heatingmeans (60) is selected from the group consisting of a laser, an electronbeam gun, a resistance heater, and an induction heater.
 10. The vapordeposition apparatus of claim 9, wherein said heating means (60) is anelectron beam gun.
 11. The vapor deposition apparatus of claim 10,wherein said electron beam gun is capable of directing an electron beamacross said first material, thereby providing a scanning pattern thatincreases a temperature of an inner area (91) of said first materialabove a temperature of an outer area (92) of said first material. 12.The vapor deposition apparatus of claim 1, wherein said crucible (45) isa water-cooled copper crucible.
 13. The vapor deposition apparatus ofclaim 1, wherein said crucible further includes a bore (46) therethroughwhich a solid piece of said second material (30) may be fed.
 14. Thevapor deposition apparatus of claim 1, wherein said crucible (45)further includes a replenishment means for replenishing said vapordeposition source.
 15. The vapor deposition apparatus of claim 1,wherein said refractory material is a rare earth metal.
 16. The vapordeposition apparatus of claim 1, wherein said refractory materialcomprises between about 33 and 76 atomic percent of said first material.17. The vapor deposition apparatus of claim 1, wherein said refractorymaterial is selected form the group consisting of zirconium, hafnium,titanium, yttrium, chromium, rhenium, silicon, and alloys thereof. 18.The vapor deposition apparatus of claim 1, wherein said first elementand said second element are contained in an alloy, wherein said alloy isselected from the group consisting of titanium-base alloys, nickel-basealloys, iron-base alloys, and aluminum-base alloys.
 19. A vapordeposition source material for use in a vapor deposition apparatusadapted to deposit a coating (71) containing a refractory material ingreater than trace amounts, said vapor deposition source materialcomprising: a) a first material (20), said first material comprising arefractory material, said refractory material being alloyed with atleast two elements; and b) a second material (30) comprising at leasttwo elements to be evaporated to form a vapor-deposited material,wherein said two elements in said second material (30) that are to beevaporated are the same as said two elements contained in said firstmaterial.
 20. The vapor deposition source material of claim 19, whereinsaid two elements in said first material (20) are present in a firstatomic ratio, and wherein said two elements in said second material (30)that are to be evaporated are present in a second atomic ratio that isapproximately the same as said first atomic ratio.
 21. The vapordeposition source material of claim 20, wherein said first atomic ratiois approximately 1:1.
 22. The vapor deposition source material of claim21, wherein said two elements in said first material are nickel andaluminum.
 23. The vapor deposition source material of claim 19, whereinsaid refractory material is selected form the group consisting ofzirconium, hafnium, titanium, yttrium, chromium, rhenium, silicon, andalloys thereof.
 24. The vapor deposition source material of claim 19,wherein said first element and said second element are contained in analloy, wherein said alloy is selected from the group consisting oftitanium-base alloys, nickel-base alloys, iron-base alloys, andaluminum-base alloys.
 25. A vapor deposition apparatus (10) adapted todeposit a vapor-deposited coating (71) containing a refractory elementin greater than trace amounts, said vapor deposition apparatuscomprising: a) a vapor deposition source material, said vapor depositionsource material comprising a first material (20), said first materialcomprising a refractory material, said refractory material being alloyedwith at least two elements, and a second material (30) comprising atleast two elements to be evaporated to form a vapor-deposited material,wherein said two elements in said second material (30) that are to beevaporated are the same as said two elements contained in said firstmaterial (20); b) a crucible (45) having an open top, said cruciblebeing capable of containing said vapor deposition source, wherein saidfirst material (20) and said second material (30) are disposed in saidchamber such that said first material is positioned over said secondmaterial and at least partially covers said second material; c) a basematerial (50) located vertically above said open top; and d) at leastone heating means (60), said heating means being capable of supplyingsufficient heat to create a molten zone (55) in said first material(20), wherein said molten zone (55) contacts said second material,thereby creating a second molten zone (56) in said second material (30),whereby said two elements in said second material (30) and saidrefractory material are evaporated from said crucible (45), therebyforming a vapor stream that impinges upon said base material (50) andcondenses thereon, thereby forming said vapor-deposited coating (71)containing said refractory material in greater than trace amounts, saidthird material, and said fourth material.
 26. The vapor depositionapparatus (10) of claim 25, further including an airtight enclosure(12), said airtight enclosure being capable of being evacuated, whereinsaid crucible (45), said first material (20), said second material (30),said heating means (60), and said base material (50) are disposed withinsaid airtight enclosure, whereby said vapor-deposited coating may bedeposited in the absence of potential contaminants or reactants.
 27. Thevapor deposition (10) apparatus of claim 26, further including a meansfor evacuating said airtight enclosure.
 28. The vapor depositionapparatus of claim 26, wherein said means for evacuating said airtightenclosure is a combination of staged mechanical pumps, cryogenic pumps,turbomolecular pumps, and diffusion pumps.
 29. The vapor depositionapparatus of claim 26, further including a reactive gas inlet forproviding a reactive gas to said airtight enclosure.
 30. The vapordeposition apparatus of claim 29, further including a reactive gassource coupled to said reactive gas inlet.
 31. The vapor depositionapparatus of claim 30, wherein said reactive gas is selected from thegroup consisting of oxygen, nitrogen, and methane.
 32. The vapordeposition apparatus of claim 25, wherein said heating means (60) iscapable of heating an inner area (91) and an outer area (92) of saidvapor deposition source such that said inner area (91) is heated to agreater temperature than a temperature of said outer area (92).
 33. Thevapor deposition apparatus of claim 25, wherein said heating means (60)is selected from the group consisting of a laser, an electron beam gun,a resistance heater, and an induction heater.
 34. The vapor depositionapparatus of claim 33, wherein said heating means (60) is an electronbeam gun.
 35. The vapor deposition apparatus of claim 34, wherein saidelectron beam gun is capable of directing an electron beam across saidfirst material, thereby providing a scanning pattern that increases atemperature of an inner area of said first material above a temperatureof an outer area of said first material.
 36. The vapor depositionapparatus of claim 25, wherein said crucible (45) is a water-cooledcopper crucible.
 37. The vapor deposition apparatus of claim 25, whereinsaid crucible (45) further includes a bore therethrough which a solidpiece of said second material may be fed.
 38. The vapor depositionapparatus of claim 25, wherein said crucible (45) further includes areplenishment means for replenishing said vapor deposition source. 39.The vapor deposition apparatus of claim 25, wherein said refractorymaterial is a rare earth metal.
 40. The vapor deposition apparatus ofclaim 25, wherein said refractory material comprises between about 33and 76 atomic percent of said first material.
 41. The vapor depositionapparatus of claim 25, wherein said refractory material is selected formthe group consisting of zirconium, hafnium, titanium, yttrium, chromium,rhenium, silicon, and alloys thereof.
 42. The vapor deposition apparatusof claim 25, wherein said first element and said second element arecontained in an alloy, wherein said alloy is selected from the groupconsisting of titanium-base alloys, nickel-base alloys, iron-basealloys, and aluminum-base alloys.
 43. The vapor deposition sourcematerial of claim 25, wherein said two elements in said first material(20) are present in a first atomic ratio, and wherein said two elementsin said second material (30) that are to be evaporated are present in asecond atomic ratio that is approximately the same as said first atomicratio.
 44. The vapor deposition source material of claim 43, whereinsaid first atomic ratio is approximately 1:1.
 45. The vapor depositionsource material of claim 44, wherein said two elements in said firstmaterial are nickel and aluminum.
 46. A vapor-deposited coating (71)comprising a first element, a second element, and a refractory material,wherein said refractory material comprises greater than 0.05 atomicpercent of said vapor-deposited coating.
 47. The vapor-deposited coatingof claim 46, wherein said first element is aluminum and said secondelement is nickel.
 48. The vapor-deposited coating of claim 46, whereinsaid refractory material is a rare earth metal.
 49. The vapor-depositedcoating of claim 46, wherein said refractory material is selected fromthe group consisting of zirconium, hafnium, yttrium, titanium, rhenium,silicon, chromium, and alloys thereof.
 50. A method of vapor-depositinga coating on a base material (50), said coating comprising at least twoelements and a refractory material, wherein said refractory materialcomprising greater than 0.05 atomic percent of said vapor-depositedcoating, the method comprising the steps of: a) providing a sourcematerial, said source material comprising a first material (20), saidfirst material comprising at least two elements, said refractory elementbeing alloyed therewith, and a second material, said second material(30) comprising at least two elements; b) placing said source materialin a crucible (45) such that said first material is positioned over saidsecond material and at least partially covers said second material; c)providing a base (50) upon which said vapor-deposited coating is to bedeposited; d) positioning said base vertically above an opening in thecrucible (45); and e) heating said first material (20), thereby creatinga molten zone (55) in said first material (20), wherein said molten zonecontacts said second material (30), thereby creating a second moltenzone (56) within said second material (30), wherein said two elements insaid second material (30) are transported through said molten zone (55),wherein said refractory material and said two elements in said secondmaterial (30) are evaporated from said source material and are condensedupon said base material (50), thereby forming said vapor-depositedcoating (71).
 51. The method of claim 50, wherein the step of providinga source material further includes selecting a refractory material fromthe group consisting of zirconium, hafnium, yttrium, titanium, rhenium,silicon, chromium, and alloys thereof.
 52. The method of claim 50,wherein the step of heating said first material further including thestep of heating an inner area (91) and an outer area (92) of said sourcematerial such that said inner area (91) is heated to a greatertemperature than a temperature of said outer area (92).
 53. A method ofvapor-depositing (71) a coating on a base material (50), said coatingcomprising at least two elements and a refractory material, wherein saidrefractory material comprising greater than 0.05 atomic percent of saidvapor-deposited coating, the method comprising the steps of: a)selecting a vapor-deposition source material, wherein said vapordeposition source material comprises a first material (20), said firstmaterial comprising a refractory material, said refractory materialbeing alloyed with at least two elements, and a second material (30)comprising at least two elements to be evaporated to form avapor-deposited material, wherein said two elements in said secondmaterial (30) that are to be evaporated are the same as said twoelements contained in said first material (20); b) placing saidvapor-deposition source material in a crucible (45) such that said firstmaterial (20) is positioned over said second material (30) and at leastpartially covers said second material (30); c) providing a base (50)upon which said vapor-deposited coating (71) is to be deposited; d)positioning said base (50) vertically above an opening in the crucible(45); and e) heating said first material (20), thereby creating a moltenzone (55) in said first material (20), wherein said molten zone (55)contacts said second material (30), thereby creating a second moltenzone (55) within said second material (30), wherein said two elements insaid second material (30) are transported through said molten zone (55),wherein said refractory material and said two elements in said secondmaterial (30) are evaporated from said source material and are condensedupon said base material (50), thereby forming said vapor-depositedcoating (71).
 54. The method of claim 53, wherein the step of providinga source material further includes selecting a refractory material fromthe group consisting of zirconium, hafnium, yttrium, titanium, rhenium,silicon, chromium, and alloys thereof.
 55. The method of claim 53,wherein the step of heating said first material (20) further includingthe step of heating an inner area (91) and an outer area (92) of saidsource material such that said inner area (91) is heated to a greatertemperature than a temperature of said outer area (92).